I am trying to setup a network that includes a EtherChannel link between two Cisco Layer 3 switches (Catalyst 3750). I am using a collapsed core hieriarchical network.  The picture above is my topology. On my layer 2 access switches (S1, S2, S3) I have several hosts connected right now, on several VLANs. My issue tho is that an host on for example S2, can't talk with L3-1 through the EtherChannel between L3-1 and L3-2. I've tried making it a Layer 3 EtherChannel with IP's, and I can ping across, but it's like it wont propagate my VLAN tagged traffic. Example: I connect HOST-A to L3-1 on interface GigabitEthernet2/0/1. I make GigabitEthernet2/0/1 switchport access on VLAN 20. HOST-B is connected to a switchport access VLAN 20 port on S2. HOST-B tries to ping L3-2. Succesful. HOST-B tries to ping across to L3-1 / HOST-A. Not succesful. PS. I also have HSRP set up at the Layer 3 switches, for all my VLANs. Also I have a Main Windows Server 2016 Domain Controller connected to L3-1 and a Backup connected to L3-2. Let me know if you need the IP scope. I appreciate all help! I just want to know what I have to think of/be sure is working, to make this network work. Any help that can advise me on what to do to get all the way out to the WAN, and so that my hosts on S1, S2 and S3 can connect to the internet is also appreciated.